1. Field of the Invention
This invention relates to a spectrally sensitized silver halide photographic emulsion and in particular, to a supersensitized silver halide photographic emulsion and, moreover, it is concerned with a process for the production of a supersensitized photographic emulsion, which process is suitable for obtaining good "color balance" and high sensitivity of a panchromatically sensitized or orthchromatically sensitized emulsion without deteriorating the stability thereof. To determine whether the color balance in the case of photographing with a light source, for example, a tungsten lamp, is exact or not a neutral grey object (having a constant value of spectral reflection factor or transmissivity over a range of visible wavelengths) is photographed under a tungsten light source, the coordinates of the reproduced color on the C. I. E. chromaticity diagram (see Theory of Color Reproduction, translated by Mawatari Tsutomu and Kokushi Tatsuro, 1971, p 10-26 and p 160-162) are determined and this point is compared with the point corresponding to the light source on the C. I. E. chromaticity diagram.
2. Description of the Prior Art
In the technique of producing silver halide photographic emulsions, it has been desired to sensitize spectrally these emulsions as effectively as possible and many studies for improvements have been made. In lithographic light-sensitive materials or color print light-sensitive materials, photographic emulsions capable of providing not only a high sensitivity but also a high contrast image have been desired. Silver chlorobromide emulsions or silver chloroiodobromide emulsions, in general, are capable of providing a higher contrast image than silver iodobromide emulsions and are superior in that there are no particular problems in the progress of chemical ripening or development. That is to say, development of silver iodobromide emulsions progresses more slowly and a lower contrast image as compared with silver chlorobromide emulsions and silver chloroiodobromide emulsions is obtained. In addition to the step of preparing an emulsion, silver iodobromide emulsions require a long water washing step because chemical ripening is difficult to progress unless water washing is carried out prior to chemical ripening or second ripening.